PROTEASE ACTIVITY ASSOCIATED WITH OCCLUSION BODY PREPARATIONS OF AN ENTOMOPOXVIRUS FROM MELANOPLUS-SANGUINIPES

An alkaline protease, associated with Melanoplus sanguinipes entomopoxvirus occlusion body preparations, was characterized. The protease had a pH optimum between 8 and 9 and a temperature optimum between 45 and 50°C. Protease activity was inhibited by phenylmethylsulfonyl fluoride, an inhibitor of serine proteases. The protease was shown to have trypsin-like activity based on the hydrolysis of a trypsin-specific synthetic substrate and inhibition by a trypsin-specific inhibitor. The protease was inactivated by heat treatment above 60°C. Heat treatment (>70°C) inhibited complete dissolution of the occlusion bodies and the release of virions in alkaline dissolution buffer. In dissolution buffer, the occlusion body matrix protein, spheroidin (108.8 kDa), was degraded into smaller polypeptides. © 1991.